write envoy filter using wasm langu

[Jenny M]

Hey,

we need to create an envoy filter using wasm (not lua), there is few language that supporting it.

• assamblyscript
• tiny-go
• rust
• c++

we need to do some auth processing/header modification, serialisations / deserialisations etc, my question is which language has the most supporting libs for wasm ?

the reason that Im asking that is that I start with tiny-go and found that many feature/libs of go is missing which make the dev very difficult...

thanks!

[Zizon Qiu]

Nowadays, it is pretty straightforward to interoperate through the Envoy WASM system,

just export and import whatever you need in your preferred WASM language.

see: 

https://github.com/proxy-wasm/proxy-wasm-cpp-host/blob/master/include/proxy-wasm/wasm.h

https://github.com/proxy-wasm/proxy-wasm-cpp-host/blob/master/include/proxy-wasm/exports.h

prefix ABI functions with proxy_ will just work out.

e.g.

to use send_local_response, just declare an import function named proxy_send_local_response.

the Envoy WASM system will do the left binding for you.

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[Jenny M]

ok thanks.

In case I need to create filter which needs to run 500,000,000 calls a day and maybe more, which language I should use (from performance aspect) , it there any difference 

if i use wasm with rust /  assembly script / cpp?

[Michael P.]

Zig has excellent support for WASM. Zig is a newish language and not yet at version 1 so subject to some change between releases. Zig is looking very promising, particularly for the WebAssembly space.

Takeshi Yoneda has written a very helpful SDK with working examples at https://github.com/mathetake/proxy-wasm-zig-sdk and https://twitter.com/mathetake/status/1397896266827198469

[Zizon Qiu]

It should be little matter on which upper language to use but the WASM runtime you chose(v8/wamr/wasmtime/wavm).

To view this discussion on the web visit https://groups.google.com/d/msgid/envoy-users/1eb321e1-ef9b-43c8-acae-be3b55db83e9n%40googlegroups.com.

[Jenny M]

Thanks! in case I write the wasm in tiny-go could I choose any runtime? how should I decide which runtime to use? 

[Zizon Qiu]

Take a look at this: https://www.envoyproxy.io/docs/envoy/latest/configuration/listeners/network_filters/wasm_filter#example-configuration

Note the vm_config.runtime. 

Docs about this field:

https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/wasm/v3/wasm.proto#envoy-v3-api-msg-extensions-wasm-v3-pluginconfig

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